Deformation-based mapping of volume change from serial brain MRI in the presence of local tissue contrast change

This paper is motivated by the analysis of serial structural magnetic resonance imaging (MRI) data of the brain to map patterns of local tissue volume loss or gain over time, using registration-based deformation tensor morphometry. Specifically, we address the important confound of local tissue contrast changes which can be induced by neurodegenerative or neurodevelopmental processes. These not only modify apparent tissue volume, but also modify tissue integrity and its resulting MRI contrast parameters. In order to address this confound we derive an approach to the voxel-wise optimization of regional mutual information (RMI) and use this to drive a viscous fluid deformation model between images in a symmetric registration process. A quantitative evaluation of the method when compared to earlier approaches is included using both synthetic data and clinical imaging data. Results show a significant reduction in errors when tissue contrast changes locally between acquisitions. Finally, examples of applying the technique to map different patterns of atrophy rate in different neurodegenerative conditions is included.     

Super‐macroporous dextran cryogels via UV‐induced crosslinking: synthesis and characterization

Cryogenic treatment and UV irradiation were exploited for the preparation of super‐macroporous cryogels from non‐modified high‐molar‐mass dextran. The photo‐crosslinking process was initiated by (4‐benzoylbenzyl)trimethylammonium chloride and N,N′‐methylenebisacrylamide (BAAm) was used as a crosslinking agent. Gel fraction yield and degree of swelling of the dextran cryogels were determined gravimetrically. Cryogel morphology and mechanical properties were studied using environmental scanning electron microscopy and dynamic rheological measurements, respectively. The effects of dextran concentration in the initial polymer solution, polymer molar mass and BAAm content on the crosslinking efficacy, physico‐mechanical properties and morphology of the cryogels were evaluated. The dextran cryogels were assessed as carriers of the model water‐soluble drug metoprolol. © 2017 Society of Chemical Industry     

Environmental Stress‐Cracking Resistance of LDPE/EVA Blends

Blends of low‐density polyethylene with random copolymers of ethylene and vinyl acetate (PE/EVA) are studied with respect to their environmental stress‐cracking resistance (ESCR) using the Bell‐telephone test. This system shows the shortest time to failure in the ESCR test after annealing at 50 °C in a stress‐cracking agent (Igepal solution) compared with that in the tests conducted at 30 and 70 °C. The increase of the time to failure at 70 °C as compared with that at 50 °C is probably the result of the semicrystalline proportion of EVA melting. Transmission electron microscopy images (see Figure) reveal that EVA particles are molten and deformed in bending direction of the sample at 70 °C in contrast to samples annealed at 50 and 30 °C. TEM pictures of a failed sample during the test conducted at 50 °C indicate that EVA particles can stop crack propagation.

TEM image of PE/EVA‐5.4 after 1 000 h in ESCR test conditions at 70 °C.     

Control of the spectral position of dichromated gelatin reflection holograms

Dichromated gelatin (DCG) is one of the best light-sensitive materials for holographic recording. However, strict technological control should be observed during deposition, gelation, and drying of DCG plates and the chemical processing of the recorded structures. Usually, for reflection holograms the gelatin layer should be sealed in order to protect it from ambient humidity, which affects the value and position of the reflection maximum. Herein we give three different recipes for tuning the reflection maximum from 430 to 700 nm by swelling the hologram thickness with a filler material that is commercially available. The mechanism of the hologram swelling, which changes the period of the recorded holographic structure, is also briefly discussed.     

Poly(ethoxytriethyleneglycol acrylate) cryogels as novel sustained drug release systems for oral application

Novel temperature sensitive cryogels of poly(ethoxytriethyleneglycol acrylate) (PETEGA), with in situ entrapped active substance, are synthesized employing the UV irradiation technique and tested as matrix for controlled release of the hydrophilic drug verapamil hydrochloride. PETEGA cryogels are non-toxic materials and, due to the macroporous structure, exhibit a reversible, ultra-rapid volume phase transition at temperature ca. 31 °C. Carriers based on PETEGA cryogels possess sustained release of verapamil hydrochloride over a period of more than 8 h, which is attributed to the hydrophobic state of the polymer network at physiological temperature and the method of drug immobilization. Drug release characteristics of PETEGA cryogels are compared with another cryogel systems, based on polyacrylamide (PAAm), poly(N-isopropylacrylamide) (PNIPAAm) and poly(2-hydroxyethyl methacrylate) (PHEMA), obtained via the same method.     

Tradeoffs in the complexity of backdoors to satisfiability: dynamic sub-solvers and learning during search

There has been considerable interest in the identification of structural properties of combinatorial problems that lead to efficient algorithms for solving them. Some forms of structure, such as properties of the underlying constraint graph, are “easily” identifiable. Others, such as backdoor sets, are of interest because they capture key aspects of state-of-the-art constraint solvers as well as of many real-world problem instances. While backdoors were originally introduced to capture propagation based simplification mechanisms of solvers, they have recently been studied also in the context of tractable syntactic classes such as 2CNF and Horn. These syntactic classes, however, do not capture key aspects of solvers such as empty clause (i.e., violated constraint) detection. We show that incorporating inconsequential sounding features such as empty clause detection has a dramatic impact on both the complexity of finding a backdoor of size k (which becomes harder in the worst case) and on the size of the resulting backdoor (which can become arbitrarily smaller). Empirically, we show that commonly employed polynomial-time “dynamic” constraint propagation mechanisms, such as unit propagation, pure literal elimination, and probing, often lead to much smaller backdoor sets in real-world domains than “statically” defined classes such as Horn and RHorn, thereby capturing structure much more succinctly. We also reveal the inherent limits of the simpler concept of deletion backdoors, specifically by looking at renamable Horn sub-formulas. Finally, we extend the notion of backdoors to incorporate learning during search—a key aspect of nearly all state-of-the-art systematic SAT solvers—and show, both theoretically and empirically, that this drastically reduces the size of the resulting backdoor set. Our results suggest that structural notions explored for designing efficient algorithms for combinatorial problems should capture both statically and dynamically identifiable properties of the combinatorial problem being solved.     

Determination of Triacylglycerol Classes and Molecular Species in Seed Oils with High Content of Linoleic and Linolenic Fatty Acids

Soya bean and linseed oils were analysed by successive application of silver-ion and reversed-phase thin-layer chromatography and densitometry. Direct quantitative determination of all the 20 possible triacylglycerol (TAG) classes including critical pairs (SD₂+S₂T; M₂T+D₃; SDT+MDT; ST₂+MT₂) was performed. TAG molecular species down to 0·1% (32 in soya bean oil and 26 in linseed oil) were identified and quantified. The detection limit was 0·2 μg and the standard deviation between 0·1% and 1·0% for silver ion thin-layer chromatography (TLC) and between 0.1% and 3.9% for reversed-phase TLC determinations. The accuracy of the analysis was confirmed by the good agreement between the quantitative results for the fatty acid composition as determined by gas chromatography and as calculated from the densitometric data for the TAG composition.     

Hormonomic Changes Driving the Negative Impact of Broomrape on Plant Host Interactions with Arbuscular Mycorrhizal Fungi

Belowground interactions of plants with other organisms in the rhizosphere rely on extensive small-molecule communication. Chemical signals released from host plant roots ensure the development of beneficial arbuscular mycorrhizal (AM) fungi which in turn modulate host plant growth and stress tolerance. However, parasitic plants have adopted the capacity to sense the same signaling molecules and to trigger their own seed germination in the immediate vicinity of host roots. The contribution of AM fungi and parasitic plants to the regulation of phytohormone levels in host plant roots and root exudates remains largely obscure. Here, we studied the hormonome in the model system comprising tobacco as a host plant, Phelipanche spp. as a holoparasitic plant, and the AM fungus Rhizophagus irregularis. Co-cultivation of tobacco with broomrape and AM fungi alone or in combination led to characteristic changes in the levels of endogenous and exuded abscisic acid, indole-3-acetic acid, cytokinins, salicylic acid, and orobanchol-type strigolactones. The hormonal content in exudates of broomrape-infested mycorrhizal roots resembled that in exudates of infested non-mycorrhizal roots and differed from that observed in exudates of non-infested mycorrhizal roots. Moreover, we observed a significant reduction in AM colonization of infested tobacco plants, pointing to a dominant role of the holoparasite within the tripartite system.     

Drug transport in stimuli responsive acrylic and methacrylic interpenetrating polymer networks

The interpenetrating polymer networks (IPNs) are recently gaining attention as sustained drug delivery systems because they could ensure a proper combination of functionality and network density to control the drug release profiles. This study aims to reveal how the functionality of two IPNs based on polyacrylamide and respectively poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) influences their smart behavior as well as their properties as delivery systems of the cationic drug verapamil hydrochloride (VPM). The “extra” α‐methyl group of PMAA results into a loss of the temperature sensitivity in the studied region and changes the pH responsivity of the PMAA/PAAM IPNs as compared to the PAA/PAAM IPNs. Moreover, the VPM diffusion in both IPNs depends on their composition due to the change in their functionality as well as of their network density. The “extra” α‐methyl group of PMAA defines its enhanced hydrophobicity and hence influences the VPM diffusion mechanism. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45380.     

Design and study of the potential of crosslinked cationic polymers as drug delivery systems for dermal application

Crosslinked carriers based on cationic monomer [2‐(acryloyloxy)ethyl]trimethylammonium chloride or 2‐(dimethylamino)ethyl methacrylate were developed and investigated as new platform for ibuprofen transdermal delivery. Series of networks of varied composition and structure were synthesized and characterized by FTIR spectroscopy and following swelling kinetics in different solvents. Dermal safety tests to examine the skin irritation and sensitization potential of the network films were performed in vivo. Chosen network compositions were loaded with ibuprofen by swelling in its ethanol solution. The structures of the drug carriers were investigated by scanning electron microscopy. Ibuprofen release from the developed drug delivery systems was followed in phosphate buffer solution at 37 °C. The investigation proved the feasibility of the developed cationic copolymer networks as effective platforms with modified ibuprofen release for potential dermal application. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46420.